Radio terminal, processor, and method for performing cell reselection

ABSTRACT

A user equipment receives an MBMS service provided using SC-PTM transmission. The user equipment performs a cell reselection operation of selecting a cell to be used as a serving cell of the user equipment while the user equipment is in an RRC idle mode. In the cell reselection operation, the user equipment selects, as the serving cell, a cell having a highest ranking determined based on a radio quality and an offset from among a plurality of cells. In the cell reselection operation, when the user equipment is in an enhanced coverage, the user equipment uses an infinite offset as the offset to be applied to a cell where the MBMS service is provided by the SC-PTM transmission, in response to a predetermined condition for the SC-PTM transmission being satisfied, when the user equipment goes out of the enhanced coverage, stop using the infinite offset.

RELATED APPLICATION

This application is a continuation application of internationalapplication PCT/JP2018/003615, filed Feb. 2, 2018, which claims thebenefit of U.S. Provisional Application No. 62/454,185 (filed on Feb. 3,2017), the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a radio terminal and a base stationfor a mobile communication system.

BACKGROUND

In 3GPP (Third Generation Partnership Project), which is a projectaiming to standardize a mobile communication system, the specificationsof MBMS (Multimedia Broadcast Multicast Service) transmission have beenlaid out to provide a radio terminal with a multicast/broadcast service.MBMS transmission schemes have two transmission schemes: MBSFN(Multicast Broadcast Single Frequency Network) and SC-PTM (Single CellPoint-To-Multipoint).

Meanwhile, radio terminals meant for MTC (Machine Type Communication)and IoT (Internet of Things) services, in which communication isperformed without human intervention, have been studied. Such a radioterminal is required to achieve low cost, wide coverage area, and lowpower consumption. For this reason, in 3GPP, a new category of radioterminals having a transmission and reception bandwidth limited only toa part of the system transmission and reception band has been specified.To such a new category of radio terminals, an enhanced coverage functionincluding repetition and the like is applied.

SUMMARY

A user equipment according to an embodiment receives an MBMS serviceprovided using SC-PTM transmission. The user equipment comprises aprocessor and a memory coupled to the processor. The processor isconfigured to perform a cell reselection operation of selecting a cellto be used as a serving cell of the user equipment while the userequipment is in an RRC idle mode. The processor is configured to: in thecell reselection operation, select, as the serving cell, a cell having ahighest ranking determined based on a radio quality and an offset fromamong a plurality of cells. The processor is configured to, in the cellreselection operation, when the user equipment is in an enhancedcoverage, use an infinite offset as the offset to be applied to a cellwhere the MBMS service is provided by the SC-PTM transmission, inresponse to a predetermined condition for the SC-PTM transmission beingsatisfied. The processor is configured to, in the cell reselectionoperation, when the user equipment goes out of the enhanced coverage,stop using the infinite offset.

An apparatus according to an embodiment is provided in a user equipmentfor receiving an MBMS service provided using SC-PTM transmission. Theapparatus comprises a processor and a memory coupled to the processor.The processor is configured to perform a cell reselection operation ofselecting a cell to be used as a serving cell of the user equipmentwhile the user equipment is in an RRC idle mode. The processor isconfigured to: in the cell reselection operation, select, as the servingcell, a cell having a highest ranking determined based on a radioquality and an offset from among a plurality of cells. The processor isconfigured to, in the cell reselection operation, when the userequipment is in an enhanced coverage, use an infinite offset as theoffset to be applied to a cell where the MBMS service is provided by theSC-PTM transmission, in response to a predetermined condition for theSC-PTM transmission being satisfied. The processor is configured to, inthe cell reselection operation, when the user equipment goes out of theenhanced coverage, stop using the infinite offset.

A method according to an embodiment is a method for use in a userequipment for receiving an MBMS service provided using SC-PTMtransmission. The method comprises performing a cell reselectionoperation of selecting a cell to be used as a serving cell of the userequipment while the user equipment is in an RRC idle mode; in the cellreselection operation, selecting, as the serving cell, a cell having ahighest ranking determined based on a radio quality and an offset fromamong a plurality of cells; in the cell reselection operation, when theuser equipment is in an enhanced coverage, using an infinite offset asthe offset to be applied to a cell where the MBMS service is provided bythe SC-PTM transmission, in response to a predetermined condition forthe SC-PTM transmission being satisfied; and in the cell reselectionoperation, when the user equipment goes out of the enhanced coverage,stopping using the infinite offset.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of an LTE system(mobile communication system) according to an embodiment.

FIG. 2 is a diagram illustrating a network configuration for MBMSaccording to the embodiment.

FIG. 3 is a diagram illustrating a configuration of a UE (radioterminal) according to the embodiment.

FIG. 4 is a diagram illustrating a configuration of an eNB (basestation) according to the embodiment.

FIG. 5 is a diagram illustrating a protocol stack of a radio interfacein the LTE system according to the embodiment.

FIG. 6A and FIG. 6B are diagrams each illustrating a channelconfiguration of a downlink of the LTE system according to theembodiment.

FIG. 7 is a diagram illustrating a configuration of a radio frame of theLTE system according to the embodiment.

FIG. 8 is a flowchart illustrating an operation example of SC-PTMaccording to the embodiment.

FIG. 9 is a diagram illustrating an SIB 20 according to the embodiment.

FIG. 10 is a diagram illustrating MBMS control information in SC-MCCHaccording to the embodiment.

FIG. 11 is a diagram illustrating a downlink physical channel for aneMTC UE according to the embodiment.

FIG. 12 is a flowchart illustrating a random access procedure for aneMTC UE and an NB-IoT UE according to the embodiment.

FIG. 13 is a diagram illustrating an operation scenario according to afirst embodiment.

FIG. 14 is a diagram illustrating an SIB according to the firstembodiment.

FIG. 15 is a flowchart illustrating an example of an operation flow of aUE according to the first embodiment.

FIG. 16 is a flowchart illustrating an example of an operation flow ofthe UE according to a modification of the first embodiment.

FIG. 17 is a diagram illustrating an example of an operation accordingto the second embodiment.

FIG. 18A and FIG. 18B are diagrams each illustrating an example of anoperation according to a modification of the second embodiment.

FIG. 19 is a diagram illustrating a case where a stop indication istransmitted by an MAC CE according to a third embodiment.

FIG. 20A, FIG. 20B, and FIG. 20C are diagrams each illustrating anexample of an operation according to the third embodiment.

DESCRIPTION OF THE EMBODIMENT

(Mobile Communication System)

The configuration of the mobile communication system according to theembodiment will be described. The mobile communication system accordingto the embodiment is an LTE (Long Term Evolution) system whosespecifications are defined in 3GPP. FIG. 1 is a diagram illustrating aconfiguration of the LTE system according to the embodiment. FIG. 2 is adiagram illustrating a network configuration for MBMS.

As illustrated in FIG. 1, the LTE system includes a radio terminal (UE:User Equipment) 100, a radio access network (E-UTRAN: Evolved-UMTSTerrestrial Radio Access Network) 10, and a core network (Evolved PacketCore) 20. The E-UTRAN 10 and the EPC 20 configure a network of the LTEsystem.

The UE 100 is a mobile communication device. The UE 100 performs radiocommunication with the eNB 200 that manages the cell (serving cell) inwhich the UE 100 exists.

The E-UTRAN 10 includes base stations (evolved Node-Bs) 200. The eNBs200 are connected to each other via an X2 interface. The eNB 200 managesone or a plurality of cells and performs radio communication with the UE100 that has established connection with a cell of the eNB 200. The eNB200 has a radio resource management (RRM) function, a routing functionof user data (hereinafter referred to simply as “data”), a measurementcontrol function for mobility control/scheduling, and the like. “Cell”is used as a term indicating the smallest unit of radio communicationarea. “Cell” is also used as a term indicating a function or resourcefor performing radio communication with the UE 100.

The EPC 20 includes a mobility management entity (MME) and a servinggateway (S-GW) 300. The MME performs various mobility control and thelike for the UE 100. The S-GW performs data transfer control. TheMME/S-GW 300 is connected to the eNB 200 via an S1 interface.

Network entity for MBMS will be described. The E-UTRAN 10 includes anMCE (Multi-Cell/Multicast Coordinating Entity) 11. The MCE 11 isconnected to the eNB 200 via an M2 interface. The MCE is connected tothe MME 300 via an M3 interface (see FIG. 2). The MCE 11 performs MBSFNradio resource management/allocation and the like. Specifically, the MCE11 performs scheduling of MBSFN transmission. On the other hand, thescheduling of the SC-PTM transmission is performed by the eNB 200.

The EPC 20 includes an MBMS GW (MBMS Gateway) 21. The MBMS GW 21 isconnected to the eNB 200 via an M1 interface. The MBMS GW 21 isconnected to the MME 300 via an Sm interface. The MBMS GW 21 isconnected to the BM-SC 22 via an SG-mb and SGi-mb interfaces (see FIG.2). The MBMS GW 21 performs IP multicast data transmission, sessioncontrol and the like to the eNB 200.

The EPC 20 includes a BM-SC (Broadcast Multicast Service Center) 22. TheBM-SC 22 is connected to the MBMS GW 21 via the SG-mb and SGi-mbinterfaces. The BM-SC 22 is connected to the P-GW 23 via an SGiinterface (see FIG. 2). The BM-SC 22 manages and allocates TMGI(Temporary Mobile Group Identity) and the like.

Further, a GCS AS (Group Communication Service Application Server) 31 isprovided in a network (that is, the Internet) outside the EPC 20. TheGCS AS 31 is an application server for group communication. The GCS AS31 is connected to the BM-SC 22 via an MB2-U interface and an MB 2-Cinterface. The GCS AS 31 is connected to the P-GW 23 via the SGiinterface. The GCS AS 31 performs management of groups and datadistribution etc. in group communication.

FIG. 3 is a diagram illustrating the configuration of the UE 100 (radioterminal) according to the embodiment. As illustrated in FIG. 3, the UE100 includes a receiver 110, a transmitter 120, and a controller 130.

The receiver 110 performs various types of reception under the controlof the controller 130. The receiver 110 includes antennas and areceiving machine. The receiving machine converts the radio signalreceived by the antennas into a baseband signal (reception signal) andoutputs the baseband signal to the controller 130.

The transmitter 120 performs various transmissions under the control ofthe controller 130. The transmitter 120 includes antennas and atransmitting machine. The transmitting machine converts a basebandsignal (transmission signal) output from the controller 130 into a radiosignal and transmits the radio signal from the antennas.

The controller 130 performs various controls in the UE 100. Thecontroller 130 includes a processor and a memory. The memory storesprograms executed by the processor and information used for processingby the processor. The processor includes a baseband processor thatperforms modulation and demodulation, encoding, decoding, and the likeof the baseband signal and a CPU (Central Processing Unit) that performsvarious processes by executing programs stored in the memory. Theprocessor may include a codec that performs encoding/decodingaudio/video signals. The processor executes various processes to bedescribed later.

FIG. 4 is a diagram illustrating a configuration of an eNB (basestation) according to the embodiment. As illustrated in FIG. 4, the eNB200 includes a transmitter 210, a receiver 220, a controller 230, and abackhaul communication unit 240.

The transmitter 210 performs various transmissions under the control ofthe controller 230. The transmitting unit 210 includes antennas and atransmitting machine. The transmitting machine converts a basebandsignal (transmission signal) outputted by the controller 230 into aradio signal and transmits the radio signal from the antennas.

The receiver 220 performs various types of reception under the controlof the controller 230. The receiver 220 includes antennas and areceiving machine. The receiving machine converts the radio signalreceived by the antennas into a baseband signal (received signal) andoutputs the baseband signal to the controller 230.

The controller 230 performs various controls in the eNB 200. Thecontroller 230 includes a processor and a memory. The memory storesprograms executed by the processor and information used for processingby the processor. The processor includes a baseband processor thatperforms modulation and demodulation, encoding, decoding, and the likeof the baseband signal and a CPU that performs various processes byexecuting programs stored in the memory. The processor executes variousprocesses to be described later.

The backhaul communication unit 240 is connected to the adjacent eNB viathe X2 interface. The backhaul communication unit 240 is connected tothe MME/S-GW 300 via the S1 interface. The backhaul communication unit240 is used for communication performed on the X2 interface,communication performed on the S1 interface, and the like. The backhaulcommunication unit 240 can also be used for communication on the M1interface and for communication on the M2 interface.

FIG. 5 is a diagram illustrating a protocol stack of a radio interfacein the LTE system. As illustrated in FIG. 5, the radio interfaceprotocol is divided into the first layer to the third layer of the OSIreference model. The first layer is a physical (PHY) layer. The secondlayer includes a MAC (Medium Access Control) layer, an RLC (Radio LinkControl) layer, and a PDCP (Packet Data Convergence Protocol) layer. Thethird layer includes an RRC (Radio Resource Control) layer.

The physical layer performs coding/decoding, modulation/demodulation,antenna mapping/demapping, and resource mapping/demapping. Between thephysical layer of the UE 100 and the physical layer of the eNB 200, dataand control signals are transmitted via the physical channel.

The MAC layer performs priority control of data, retransmissionprocessing by HARQ (Hybrid ARQ), and the like. Between the MAC layer ofthe UE 100 and the MAC layer of the eNB 200, data and control signalsare transmitted via the transport channel. The MAC layer of the eNB 200includes a scheduler. The scheduler determines the uplink and downlinktransport format (Transport Block Size, Modulation and Coding Scheme(MCS)) and the allocated resource block to the UE 100.

The RLC layer uses the functions of the MAC layer and the physical layerto transmit data to the RLC layer on the receiving side. Between the RLClayer of the UE 100 and the RLC layer of the eNB 200, data and controlsignals are transmitted via logical channels.

The PDCP layer carries out header compression/decompression,encryption/decryption.

The RRC layer is defined only in the control plane handling the controlsignal. Messages (RRC messages) for various configurations aretransmitted between the RRC layer of the UE 100 and the RRC layer of theeNB 200. The RRC layer controls logical channels, transport channels,and physical channels in response to establishment, reestablishment andrelease of radio bearers. If there is a connection (RRC connection)between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 isin an RRC connected mode. If there is not a connection (RRC connection)between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 isin an RRC idle state.

The NAS (Non-Access Stratum) layer located above the RRC layer performssession management, mobility management, and the like.

FIG. 6 is a diagram illustrating a channel configuration of downlink ofthe LTE system. FIG. 6(a) illustrates mapping between a logical channel(Downlink Logical Channel) and a transport channel (Downlink TransportChannel).

As illustrated in FIG. 6(a), PCCH (Paging Control Channel) is a logicalchannel for notifying paging information and system information change.The PCCH is mapped to PCH (Paging Channel) that is a transport channel.

BCCH (Broadcast Control Channel) is a logical channel for systeminformation. The BCCH is mapped to BCH (Broadcast Control Channel) and aDL-SCH (Downlink Shared Channel), both of which are transport channels.

CCCH (Common Control Channel) is a logical channel for transmissioncontrol information between the UE 100 and the eNB 200. The CCCH is usedif the UE 100 does not have an RRC connection with the network. The CCCHis mapped to the DL-SCH.

DCCH (Dedicated Control Channel) is a logical channel for transmittingindividual control information between the UE 100 and the network. TheDCCH is used if the UE 100 has an RRC connection. The DCCH is mapped tothe DL-SCH.

DTCH (Dedicated Traffic Channel) is an individual logical channel fordata transmission. The DTCH is mapped to the DL-SCH.

SC-MTCH (Single Cell Multicast Traffic Channel) is a logical channel forSC-PTM transmission. The SC-MTCH is a point-to-multipoint downlinkchannel for multicast transmitting data (MBMS) from the network to theUE 100 by using the SC-PTM transmission.

SC-MCCH (Single Cell Multicast Control Channel) is a logical channel forSC-PTM transmission. The SC-MCCH is a point-to-multipoint downlinkchannel for multicast transmitting MBMS control information for one ormore SC-MTCHs from the network to the UE 100. The SC-MCCH is used for aUE 100 that is to receive an MBMS using SC-PTM transmission or that isinterested in the reception. Further, there is only one SC-MCCH in onecell.

MCCH (Multicast Control Channel) is a logical channel for MBSFNtransmission. The MCCH is used for transmitting MBMS control informationfor MTCH from the network to the UE 100. The MCCH is mapped to an MCH(Multicast Channel) that is a transport channel.

MTCH (Multicast Traffic Channel) is a logical channel for MBSFNtransmission. The MTCH is mapped to the MCH.

FIG. 6(b) illustrates mapping between a transport channel (DownlinkTransport Channel) and a physical channel (Downlink Physical Channel).

As illustrated in FIG. 6(b), the BCH is mapped to PBCH (PhysicalBroadcast Channel).

The MCH is mapped to PMCH (Physical Multicast Channel). The MCH supportsMBSFN transmission by a plurality of cells.

The PCH and the DL-SCH are mapped to PDSCH (Physical Downlink SharedChannel). The DL-SCH supports HARQ, link adaptation, and dynamicresource allocation.

PDCCH carries resource allocation information of the PDSCH (DL-SCH,PCH), HARQ information on the DL-SCH, and the like. Further, the PDCCHcarries an uplink scheduling grant.

FIG. 7 is a diagram illustrating a configuration of a radio frame of theLTE system. In the LTE system, OFDMA (Orthogonal Frequency DivisionMultiple Access) is applied to a downlink. In the LTE system, SC-FDMA(Single Carrier Frequency Division Multiple Access) is applied to anuplink.

As illustrated in FIG. 7, the radio frame includes ten subframesarranged in a time direction. Each of the subframes includes two slotsarranged in the time direction. Each of the subframes has a length of 1ms and each of the slots has a length of 0.5 ms. Each of the subframesincludes a plurality of resource blocks (RBs) in a frequency direction,and a plurality of symbols in the time direction. Each of the resourceblocks includes a plurality of subcarriers in the frequency direction.One resource element (RE) includes one symbol and one subcarrier.Further, of radio resources (time and frequency resources) to beallocated to a UE 100, the frequency resource can be identified by aresource block, and the time resource can be identified by a subframe(or a slot).

In the downlink, a section including several symbols at the head of eachof the subframes is a region used as the PDCCH for mainly transmitting adownlink control signal. Furthermore, the remaining portion of each ofthe subframes is a region available as the PDSCH for mainly transmittingdownlink data. Further, in the downlink, an MBSFN subframe that is asubframe for MBSFN may be set.

In the uplink, both ends in the frequency direction of each subframe areregions used as the PUCCH for mainly transmitting a uplink controlsignal. The remaining portion of each subframe is a region available asthe PUSCH for mainly transmitting uplink data.

[Outline of Cell Reselection Operation]

Next, outline of cell reselection operation will be described. The UE100 under RRC idle mode measures, if a start condition is satisfied, thequality of an adjacent cell adjacent to the current serving cell, andselects, from among the cells that satisfy a selection condition, thetarget cell used as a serving cell.

Firstly, the start condition is shown as follows:

(A1) A frequency having a higher priority than the priority of thefrequency of the current serving cell

the UE 100 always measures the quality of the frequency having thehigher priority.

(A2) A frequency having a priority equal to or lower than the priorityof the frequency of the current serving cell

the UE 100 measures, if the quality of the current serving cell fallsbelow a predetermined threshold value, the quality of the frequencyhaving the equal priority or the lower priority.

Secondly, the selection condition is shown as follows:

(B1) The priority of the frequency of the adjacent cell is higher thanthe priority of the current serving cell

the UE 100 selects a cell that satisfies a relationship ofSqual>ThreshX, HighQ over a predetermined period (TreselectionRAT), or acell that satisfies a relationship of Srxlev>ThreshX, HighP over thepredetermined period (TreselectionRAT). In such a case, such criteria tobe satisfied by the adjacent cell may be referred to as “S-criteria”.

It is noted that Squal represents a cell selection quality level. Squalis calculated by Squal=Qqualmeas−(Qqualmin+Qqualminoffset)−Qoffsettemp.Qqualmeas is a quality level (RSRQ) of the adjacent cell, Qqualmin is aminimum required quality level, Qqualminoffset is a predetermined offsetregularly applied to the adjacent cell, and Qoffsettemp is an offsettemporarily applied to the adjacent cell. ThreshX, HighQ is apredetermined threshold value.

Further, Srxlev represents a cell selection reception level. Srxlev iscalculated bySrxlev=Qrxlevmeas−(Qrxlevmin+Qrxlevminoffset)−Pcompensation−Qoffsettemp.Qrxlevmeas is a reception level (RSRP) of the adjacent cell, Qrxlevminis a minimum required reception level, Qrxlevminoffset is apredetermined offset regularly applied to the adjacent cell,Pcompensation is a parameter related to an uplink capability, andQoffsettemp is an offset temporarily applied to the adjacent cell.ThreshX, HighP is a predetermined threshold value.

(B2) The priority of the frequency of the adjacent cell is the same asthe priority of the current serving cell:

the UE 100 calculates a ranking Rs of the current serving cell and aranking Rn of the adjacent cell. The UE 100 selects a cell having ahigher ranking Rn than Rs over a predetermined period (TreselectionRAT)as the target cell. In such a case, such criteria to be satisfied by theadjacent cell maybe referred to as “R-criteria”.

It is noted that Rs is calculated by Rs=Qmeas,s+QHyst−Qoffsettemp. Rn iscalculated by Rn=Qmeas,n−Qoffset−Qoffsettemp. Qmeas,s is the receptionlevel (RSRP) of the current serving cell, and Qmeas,n is the receptionlevel (RSRP) of the adjacent cell. QHyst is a hysteresis value forachieving preferential reselection of the current serving cell as thetarget cell. Qoffsettemp is an offset temporarily applied to the currentserving cell and the adjacent cell.

(B3) The priority of the frequency of the adjacent cell is lower thanthe priority of the current serving cell

the UE 100 selects, under a premise that Squal<ThreshServing, LowQ issatisfied over a predetermined period (TreselectionRAT), orSrxlev<ThreshServing, LowP is satisfied over the predetermined period(TreselectionRAT), the target cell from among the adjacent cells by amethod similar to the above described (B1).

It is noted that ThreshServing, LowQ and ThreshServing, LowP arepredetermined threshold values similarly to ThreshX, HighQ and ThreshX,HighP.

It is noted that various types of parameters used for selecting thetarget cell are included in system information (SIB; System InformationBlock) broadcast from the eNB 200. The various types of parametersinclude the priority of the frequency (cellReselectionPriority), apredetermined period (TreselectionRAT), various types of offsets(Qqualminoffset, Qrxlevminoffset, Qoffsettemp, QHyst, Qoffset), andvarious types of threshold values (ThreshX, HighQ, ThreshX, HighP,ThreshServing, LowQ, ThreshServing, LowP).

(Outline of SC-PTM Transmission)

Next, outline of SC-PTM transmission will be described. Radiotransmission schemes for MBMS include two schemes: MBSFN transmissionand SC-PTM transmission. In the MBSFN transmission, data is transmittedvia the PMCH for each MBSFN area including a plurality of cells. Incontrast, in the SC-PTM transmission, data is transmitted via the PDSCHfor each cell. In the following, a scenario in which the UE 100 performsSC-PTM reception is mainly assumed. However, MBSFN transmission may beassumed.

The UE 100 may receive the MBMS service in the RRC connected state. TheUE 100 may receive the MBMS service in the RRC idle state. In thefollowing, it is mainly assumed that the UE 100 receives the MBMSservice in the RRC idle state.

FIG. 8 is a diagram illustrating an operation example of SC-PTMtransmission.

In step S1, the UE 100 acquires a USD (User Service Description) fromthe EPC 20 via the eNB 200. The USD provides basic information on eachMBMS service. For each MBMS service, the USD includes a TMGI foridentifying the MBMS service, a frequency at which the MBMS service isprovided, and a provision start/end time of the MBMS service.

In step S2, the UE 100 receives a SIB 20 from the eNB 200 via the BCCH.The SIB 20 includes information (scheduling information) necessary foracquiring the SC-MCCH. FIG. 9 is a diagram illustrating the SIB 20. Asillustrated in FIG. 9, the SIB 20 includes sc-mcch-ModificationPeriod,sc-mcch-RepetitionPeriod, sc-mcch-Offset and sc-mcch-Subframe and thelike. The sc-mcch-ModificationPeriod represents a cycle in which thecontent of the SC-MCCH can be changed. The sc-mcch-RepetitionPeriodrepresents a transmission (retransmission) time interval of the SC-MCCHin the number of radio frames. The sc-mcch-Offset represents a scheduledradio frame offset of the SC-MCCH. The sc-mcch-Subframe represents asubframe in which the SC-MCCH is scheduled.

In step S3, the UE 100 receives MBMS control information from the eNB200 via the SC-MCCH, based on the SIB 20. MBMS control information maybe also called SCPTM configuration information (SCPTM Configuration).For the SC-MCCH transmission in the physical layer, an SC-RNTI (SingleCell RNTI) is used. FIG. 10 is a diagram illustrating the MBMS controlinformation (SC-PTM configuration information) in the SC-MCCH. TheSC-PTM configuration information includes control information applicableto the MBMS service, which is transmitted via SC-MRB (Single Cell MBMSPoint to Multipoint Radio Bearer). The SC-PTM configuration informationincludes sc-mtch-InfoList and scptmNeighbourCellList. Thesc-mtch-InfoList contains configuration for each SC-MTCH in the celltransmitting that information. The scptmNeighbourCellList is a list ofneighbour cells providing the MBMS service via the SC-MRB. Thesc-mtch-InfoList contains one or more pieces of SC-MTCH-Info. Each pieceof the SC-MTCH-Info contains information on an ongoing MBMS session(mbmsSessionInfo) to be transmitted via the SC-MRB, a G-RNTI (GroupRNTI) corresponding to the MBMS session, and sc-mtch-schedulingInfobeing DRX information for the SC-MTCH. The mbmsSessionInfo contains aTMGI and a session ID (sessionld) to identify the MBMS service. TheG-RNTI is an RNTI to identify a multicast group (specifically, SC-MTCHaddressed to a specific group). The G-RNTI is mapped to the TMGI on aone-to-one basis. The sc-mtch-schedulingInfo containsonDurationTimerSCPTM, drx-InactivityTimerSCPTM, andschedulingPeriodStartOffsetSCPTM. The schedulingPeriodStartOffsetSCPTMcontains SC-MTCH-SchedulingCycle and SC-MTCH-SchedulingOffset.

In step S4, the UE 100 receives the MBMS service (MBMS data)corresponding to the TMGI, in which the UE 100 itself is interested, viathe SC-MTCH, based on SC-MTCH-SchedulingInfo in the SC-PTM configurationinformation. In the physical layer, the eNB 200, after transmitting thePDCCH by using the G-RNTI, transmits the MBMS data via the PDSCH.

It should be noted that the control signal (signaling) described withreference to FIG. 8 is an example. Due to optimization for power savingreception or the like, part of the control signals may be omitted or theorder of the control signals may be changed.

(Overview of eMTC and NB-IoT)

Next, an overview of eMTC and NB-IoT will be described. In theembodiment, a scenario is assumed where a new category of UE 100 exists.The new category of UE 100 is a UE 100 whose transmission and receptionbandwidth is limited only to a part of the system transmission andreception band. The new UE category is referred to as, for example,category M1 and NB (Narrow Band)-IoT category. The category M1 is aneMTC (enhanced Machine Type Communications) UE. Further, the NB-IoT UEis category NB1. The category M1 limits the transmission and receptionbandwidth of the UE 100 to 1.08 MHz (that is, a bandwidth of sixresource blocks). The category M1 supports an enhanced coverage (EC)function using repetition and the like. The NB-IoT category furtherlimits the transmission and reception bandwidth of the UE 100 to 180 kHz(that is, a bandwidth of one resource block). The NB-IoT categorysupports the enhanced coverage function. The repetition is a techniqueof using a plurality of subframes to repeatedly transmit the samesignal. As an example, the system bandwidth of the LTE system is 10 MHz,of which the transmission and reception bandwidth is 9 MHz (that is, thebandwidth of 50 resource blocks). On the other hand, the category M1 ofUE 100 cannot receive a normal PDCCH because the category M1 of UE 100cannot receive a downlink radio signal transmitted with a widerbandwidth than six resource blocks. For this reason, MPDCCH (MTC-PDCCH)which is PDCCH for the MTC is introduced. For the same reason, NPDCCH(NB-PDCCH) which is PDCCH for the NB-IoT is introduced.

The enhanced coverage function may include repetition for repeatedlytransmitting the same signal. As a repetition count increases, thecoverage can be enhanced. The enhanced coverage function may includepower boosting for increasing a power density of the transmitted signal.As an example, the power density is increased by narrowband transmissionfor narrowing the frequency bandwidth of the transmitted signal. As thepower density of the transmitted signal increases, the coverage can beenhanced. The enhanced coverage function may include a lower MCStransmission for lowering the MCS to be used for the transmitted signal.The coverage can be enhanced by performing the transmission using an MCSwith a low data rate and a high error resilience.

FIG. 11 is a diagram illustrating a downlink physical channel for theeMTC UE. As illustrated in FIG. 11, the eNB 200 transmits MPDCCH withinsix resource blocks. The MPDCCH includes scheduling information forallocating PDSCH. As an example, the MPDCCH allocates PDSCH for asubframe different from the subframe in which the MPDCCH is transmitted.The eNB 200 transmits the PDSCH within six resource blocks. The eNB 200allocates PDSCHs to a plurality of subframes to perform the repetitionof the same signal. The category M1 of UE 100 identifies the allocatedPDSCH by receiving the MPDCCH and receives the data transmitted with theallocated PDSCH.

FIG. 12 is a flowchart illustrating a random access procedure for aneMTC UE and an NB-IoT UE. In an initial state of FIG. 12, the UE 100 isin an RRC idle mode. The UE 100 performs a random access procedure totransition to an RRC connected mode.

The UE 100 selects a cell of the eNB 200 as a serving cell. If the firstcell selection criteria (first S-criteria) for normal coverage are notsatisfied and the second cell selection criteria (second S-criteria) forenhanced coverage are satisfied, the UE 100 may determine that the UE100 is in the enhanced coverage. A “UE in enhanced coverage” means a UEthat is required to use an enhanced coverage function (enhanced coveragemode) to access a cell. It is noted that it is mandatory for the eMTC UEto use the enhanced coverage mode.

In step S1001, the eNB 200 transmits PRACH (Physical Random AccessChannel) related information by broadcast signaling (for example, anSIB). The PRACH related information includes various types of parametersprovided for each enhanced coverage level. As an example, a total offour levels of enhanced coverage levels 0 to 3 are defined for theenhanced coverage levels. The various types of parameters include anRSRP (Reference Signal Received Power) threshold value, a PRACHresource, and the maximum preamble transmission count. The PRACHresource includes a radio resource (time-frequency resource) and asignal sequence (preamble sequence). The UE 100 stores the receivedPRACH related information.

In step S1002, the UE 100 measures the RSRP, based on a reference signaltransmitted from the eNB 200.

In step S1003, the UE 100 compares the measured RSRP with the RSRPthreshold for each enhanced coverage level to determine the enhancedcoverage level of the UE 100. The enhanced coverage level indicates thedegree of the enhanced coverage required for the UE 100. The enhancedcoverage level is related at least to the transmission count inrepetition (that is, repetition count).

In step S1004, the UE 100 selects a PRACH resource corresponding to theenhanced coverage level of the UE 100.

In step S1005, the UE 100 uses the selected PRACH resource to transmitMsg 1 (random access preamble) to the eNB 200. The eNB 200 identifiesthe enhanced coverage level of the UE 100, based on the PRACH resourceused for the received Msg 1.

In step S1006, the eNB 200 transmits, to the UE 100, Msg 2 (randomaccess response) including scheduling information indicating the PUSCHresource allocated to the UE 100. The UE 100 can transmit the Msg 1 aplurality of times up to the maximum preamble transmission countcorresponding to the enhanced coverage level of the UE 100 until the Msg2 is normally received.

In step S1007, the UE 100 transmits Msg 3 to the eNB 200, based on thescheduling information. The Msg 3 may be an RRC Connection Requestmessage.

In step S1008, the eNB 200 transmits Msg 4 to the UE 100.

In step S1009, the UE 100 transitions to an RRC connected mode inresponse to reception of the Msg 4. Thereafter, the eNB 200 controls therepetition and the like to the UE 100, based on the identified enhancedcoverage level.

First Embodiment

A first embodiment will be described while the mobile communicationsystem as described above is assumed. In the first embodiment, ascenario is assumed in which a batch delivery of firmware or the like isperformed by SC-PTM transmission to the new category of the UE 100described above. Further, a case is mainly assumed where the UE 100 inan RRC idle mode receives an MBMS service provided by SC-PTMtransmission.

FIG. 13 is a diagram illustrating an operation scenario according to thefirst embodiment.

As illustrated in FIG. 13, in an RRC idle mode, the UE (eMTC UE orNB-IoT UE) 100 is in an enhanced coverage. Specifically, the UE 100 islocated in the enhanced coverage of a cell #1 managed by an eNB 200-1,and selects the cell #1 as the serving cell. Each of the cell #1 managedby the eNB 200-1 and a cell #2 managed by an eNB 200-2 is an SC-PTM cellwhere an MBMS service is provided by using SC-PTM transmission. A cell#3 managed by an eNB 200-3 is a non-SC-PTM cell where no MBMS service isprovided by using the SC-PTM transmission.

The UE 100 is receiving or interested in receiving the MBMS serviceprovided by using the SC-PTM transmission. A state where the UE 100 isinterested in receiving the MBMS service may be a state where the UE isnot yet to receive the MBMS service, but is configured to receive theMBMS service from a higher layer or the like.

The enhanced coverage of the cell #1 and the coverage of the cell #3geographically overlap. In this case, the UE 100 may determine that aradio quality of the cell #3 is better than a radio quality of the cell#1 and reselect the cell #3 as the serving cell. The radio quality is,for example, a reception level (RSRP). In this case, to ensure that theUE 100 receives the MBMS service, the UE 100 needs to receive the MBMSservice by unicast from the network by way of unicast communication(unicast transmission). However, to perform the unicast communication,the UE 100 needs to transition from the RRC idle mode to an RRCconnected mode. Therefore, the utilization efficiency of radio resourcesis degraded, and the power consumption of the UE 100 increases.

The first embodiment is an embodiment aiming to solve such a problem.The UE 100 according to the first embodiment receives the MBMS serviceprovided by using the SC-PTM transmission. The controller 130 of the UE100 performs a cell reselection operation of selecting a cell to be usedas the serving cell of the UE 100 while the UE 100 is in the RRC idlemode. In the cell reselection operation, the controller 130 of the UE100 selects, as the serving cell, a cell having the highest rankingdetermined based on the radio quality and the offset from among aplurality of cells. If a predetermined condition for the SC-PTMtransmission is satisfied, the controller 130 of the UE 100 configuresan infinite offset as an offset to be applied to a predetermined cell.The infinite offset may be a positive infinity (+∞) or a negativeinfinity (−∞).

The predetermined condition may be that a cell where the MBMS service isprovided by the SC-PTM transmission exists in a plurality of cells. TheUE 100 may determine whether the MBMS service is provided by the SC-PTMtransmission in the serving cell and/or a neighboring cell, based on theSIB 20 and/or SC-MCCH (for example, scptmNeighborCellList) received fromthe serving cell. The predetermined condition may be that the UE 100 isreceiving or interested in receiving the MBMS service.

The predetermined cell to which the infinite offset is applied may be acell (SC-PTM cell) where the MBMS service is provided by the SC-PTMtransmission. In this case, the infinite offset may be an offset forincreasing the ranking of the predetermined cell to the highest. As anexample, a case is assumed where a current serving cell is an SC-PTMcell and the UE 100 calculates a ranking Rs of the current serving cellwith the above-mentioned calculation formula (that is,“R_(s)=Q_(meas's)+Q_(Hyst)−Qoffset_(temp)”). In such a case, a value ofthe negative infinity is set to Qoffset_(temp) to be applied to thecurrent serving cell, so that the ranking Rs can be increased to thehighest ranking. Alternatively, Q_(Hyst) may be considered as a type ofoffset and a value of the positive infinity may be set to Q_(Hyst) to beapplied to the current serving cell.

The predetermined cell to which the infinite offset is applied may be acell (non-SC-PTM cell) where no MBMS service is provided by the SC-PTMtransmission. In this case, the infinite offset may be an offset fordecreasing the ranking of a predetermined cell to the lowest. As anexample, a case is assumed where a neighboring cell is a non-SC-PTM celland the UE 100 calculates a ranking R_(n) of the neighboring cell withthe above-mentioned calculation formula (that is,“R_(n)=Q_(meas'n)−Qofffset−Qoffset_(temp)”). In such a case, a value ofthe positive infinity is set to Qoffset and/or Qoffset_(temp) to beapplied to the neighboring cell, so that the ranking R_(n) can bedecreased to the lowest ranking.

In the first embodiment, the receiver 110 of the UE 100 may receive asystem information block (SIB) broadcast from the serving cell. The SIBmay include an infinite offset associated with a predetermined cell. TheSIB may include an infinite offset associated with a predeterminedfrequency. Alternatively, the SIB may be an infinite offset notassociated with a predetermined cell and frequency. If the infiniteoffset is not associated with a predetermined cell and frequency, theSIB may include an identifier (a grant flag) indicating that theinfinite offset may be applied to an SC-PTM cell. FIG. 14 is a diagramillustrating an SIB according to the first embodiment. As illustrated inFIG. 14, the eNB 200 broadcasts at least one of an SIB type 3 (SIB 3),an SIB type 4 (SIB 4), and an SIB type 5 (SIB 5). The SIB 3 is an SIBincluding a cell reselection parameter mainly related to a serving cell.The SIB 4 and the SIB 5 are SIBs including a cell reselection parametermainly related to a neighboring cell. The SIBs 3/4/5 may include atleast one set of a cell identifier of a predetermined cell and an offset(infinite offset) to be applied to the predetermined cell. The infiniteoffset associated with the predetermined cell may be included in theSC-MCCH or may be included in the SIB 20. The infinite offset may bepreconfigured for the UE 100.

FIG. 15 is a flowchart illustrating an example of an operation flow ofthe UE 100 according to the first embodiment.

As illustrated in FIG. 15, in step S101, the UE 100 in the RRC idle modedetermines whether the enhanced coverage function is required for the UE100 itself (that is, whether the UE 100 itself is in the enhancedcoverage). If the enhanced coverage function is not required for the UE100 itself (step S101: NO), in step S102, the UE 100 performs a normalcell reselection operation as in the “Outline of cell reselectionoperation” described above.

If the enhanced coverage function is required for the UE 100 itself(step S101: YES), in step S103, the UE 100 determines whether the UE 100is receiving or interested in receiving the MBMS service. If the UE 100is not receiving the MBMS service and is not interested in receiving theMBMS service (step S103: NO), in step S104, the UE 100 uses a ranking toselect a cell having the best radio quality. Specifically, the UE 100applies a ranking using an “S-criteria” or an “R-criteria” for theenhanced coverage to the same frequency (intra-frequency) and anotherfrequency (inter-frequency). In other words, the UE 100 in the enhancedcoverage preferentially selects a cell with the best radio quality(reception level) without considering a frequency priority. An operationin this case is similar to the operation where “(B2) The priority of thefrequency of the neighboring cell is identical to the priority of thecurrent serving cell” of the “Outline of cell reselection operation”.However, in step S104, the UE 100 performs the ranking without using theinfinite offset.

If the UE 100 is receiving or interested in receiving the MBMS service(step S103: YES), in step S105, the UE 100 may determine whether a cellwhere a desired MBMS service is provided by SC-PTM transmission existsin a plurality of cells (the serving cell and the neighboring cell). If“NO” is determined in step S105, the process proceeds to step S104. If“YES” is determined in step S105, the process proceeds to step S106.However, step S105 is not essential, and thus, may be omitted.

In step S106, the UE 100 receives, from the serving cell, the SIB (orthe SC-MCCH) including the infinite offset associated with apredetermined cell, and obtains the infinite offset. Step S106 may beexecuted before step S105. In step S107, the UE 100 selects, as theserving cell, a cell having the highest ranking determined based on theradio quality (reception level) and the offset from among the pluralityof cells. As described above, the UE 100 configures the infinite offsetas an offset to be applied to a predetermined cell if a predeterminedcondition for the SC-PTM transmission is satisfied. If there are aplurality of cells having the highest ranking, the UE 100 may select anycell from the plurality of cells having the highest ranking.

Modification of First Embodiment

A modification of the first embodiment will be described with a focus ondifferences from the first embodiment. In the modification of the firstembodiment, an operation after the UE 100 performs the cell reselectionoperation based on the ranking using the offset will be described. Themodification of the first embodiment may not be based on the firstembodiment. That is, the offset to be applied to a predetermined cellmay not be infinite.

If performing the cell reselection operation based on the ranking usingthe offset, the UE 100 may select a cell with poor radio quality as theserving cell without selecting a cell with the best radio quality as theserving cell. Under such a premise, if the UE 100 needs to performunicast communication, the UE may execute a random access procedure on acurrent serving cell, that is, the cell with poor radio quality. As aresult, since the UE 100 establishes an RRC connection with the cellwith poor radio quality, the UE 100 may not possibly perform the unicastcommunication appropriately.

The modification of the first embodiment is a modification aiming tosolve such a problem. The receiver 110 of the UE 100 according to themodification of the first embodiment receives an MBMS service providedusing SC-PTM transmission while the UE 100 is in an RRC idle mode. Thecontroller 130 of the UE 100 starts a procedure (random accessprocedure) for transitioning from the RRC idle mode to an RRC connectedmode, in response to a necessity for the UE 100 to perform the unicastcommunication. The controller 130 of the UE 100 performs a cellreselection operation of selecting a cell to be used as the serving cellof the UE 100 from among a plurality of cells at a predetermined timingbefore the UE 100 starts the random access procedure.

The predetermined timing may be a timing after the UE 100 determinesthat it is necessary to perform the unicast communication. Thecontroller 130 of the UE 100 may determine that the necessity to performthe unicast communication has occurred, in response to at least one ofconditions being satisfied, the conditions including generation ofuplink data with a higher priority than the SC-PTM, notification ofgeneration of uplink data or a control signal notified from a higherlayer (NAS), and reception of a paging. The predetermined timing may bea timing when or after the UE 100 loses interest in receiving the MBMSservice or stops receiving the MBMS service.

The predetermined timing may be a timing at which to determine toperform the random access procedure, a timing immediately before RRCConnection Request (or RRC Connection Resume Request) transmissionduring the random access procedure, or a timing immediately before arandom access preamble transmission.

The controller 130 of the UE 100 performs a cell reselection operationusing an offset for raising the ranking of the cell where the MBMSservice is provided at a timing before the predetermined timing (see thefirst embodiment). In other words, the UE 100 performs a cellreselection operation to preferentially select an SC-PTM cell in orderto receive the MBMS service in an RRC idle mode. The controller 130 ofthe UE 100 then performs a cell reselection operation without using theoffset at a predetermined timing before starting the random accessprocedure. In other words, the UE 100 performs a cell reselectionoperation excluding the above-described offset to select a cell with thebest radio quality. It is noted that the offset may take the infinitevalue as described above, or may take a finite value (for example, anoffset value such as 10 dB). Thus, the UE 100 can establish the RRCconnection with a cell with the best radio quality.

FIG. 16 is a flowchart illustrating an example of an operation flow ofthe UE 100 according to the modification of the first embodiment.

In step S151, the UE 100 in an RRC idle mode performs a cell reselectionoperation based on ranking using an offset for raising the ranking of acell (SC-PTM cell) where an MBMS service is provided. In step S152, theUE 100 receives the MBMS service provided using SC-PTM transmissionwhile the UE 100 is in the RRC idle mode.

In step S153, the UE 100 may determine whether to cancel the receptionof the MBMS service provided using the SC-PTM transmission. In otherwords, the UE 100 may determine whether the UE 100 is no longerinterested in the SC-PTM reception or whether the UE 100 cancels thereception. If canceling the SC-PTM reception (step S153: YES), in stepS154, the UE 100 cancels the SC-PTM reception, and advances the processto step S156. If continuing the SC-PTM reception (step S153: NO), the UE100 advances the process to step S155. It is noted that the processes ofstep S153 and step S154 are not essential.

In step S155, the UE 100 determines whether it is necessary to performthe unicast communication. If it is not necessary to perform the unicastcommunication (step S155: NO), the UE 100 returns the process to stepS153. If it is necessary to perform the unicast communication (stepS155: YES), the UE 100 advances the process to step S156.

In step S156, the UE 100 performs a cell reselection operation based onthe ranking not using the offset for raising the ranking of the cell(SC-PTM cell) where the MBMS service is provided. In the cellreselection operation, the UE 100 may measure a radio quality of each ofcells again to select a cell. In the cell reselection operation, the UE100 may exclude the offset from an already held measurement result ofeach of the cells to select a cell. Specifically, the UE 100 excludesthe offset only from a cell to which the offset has been applied.Alternatively, the UE 100 may hold a plurality of tables (measurementresults). Each of the tables is a table for the measurement result ofeach of the cells. The plurality of tables include a measurement resulttable where the offset is applied, a measurement result table where theoffset is not applied, and the like. If the UE 100 saves in advance themeasurement result in a table form, the UE 100 may just read the tableagain without remeasurement and recalculation, and thus, the operationis faster.

In step S157, the UE 100 performs the random access procedure on thecell selected by the cell reselection operation, and transitions fromthe RRC idle mode to an RRC connected mode. In step S158, the UE 100performs the unicast communication in the RRC connected mode. Here, theUE 100 may receive the MBMS service received in step S152 by the unicastcommunication.

Second Embodiment

A second embodiment will be described with a focus on a difference fromthe first embodiment.

As described above, the UE 100 receives the MBMS service (MBMS data)corresponding to the TMGI in which the UE 100 is interested, based onSC-MTCH-SchedulingInfo in the SC-PTM configuration information, via theSC-MTCH. In the physical layer, after transmitting the PDCCH using theG-RNTI, the eNB 200 transmits the MBMS data via the PDSCH. TheSC-MTCH-SchedulingInfo includes a DRX configuration for the SC-MTCH (forexample, onDurationTimerSCPTM, drx-InactivityTimersCSPTM, andschedulingPeriodStartOffconfiguresCPTM). On the other hand, the enhancedcoverage function includes repetition for repeatedly transmitting thesame signal (Repetition). The eNB 200 repeatedly transmits MPDCCH orNPDCCH (control information), and repeatedly transmits PDSCH (data).Therefore, the eNB 200 desirably configures a DRX cycle in which therepetition is considered, for the UE 100.

The eNB 200 according to the second embodiment provides the MBMS serviceusing the SC-PTM transmission. The controller 230 of the eNB 200configures the DRX cycle to be used for a DRX operation for the MBMSservice, for the UE 100. The transmitter 210 of the eNB 200 performs afirst repetition of repeatedly transmitting the control informationcorresponding to data belonging to the MBMS service, and a secondrepetition of repeatedly transmitting the data. The controller 230 ofthe eNB 200 configures, as the DRX cycle, a time equal to or longer thana total of a first period required for the first repetition, a secondperiod required for the second repetition, and a third period requiredto switch between the first repetition and the second repetition.

FIG. 17 is a diagram illustrating an example of an operation accordingto the second embodiment. As illustrated in FIG. 17, the eNB 200 usesthe SC-MTCH to transmit data belonging to a predetermined MBMS service(here, an MBMS service of TMGI #1) to the UE 100. In a first period T1,the eNB 200 repeatedly transmits MPDCCH or NPDCCH (referred to as “(M/N)PDCCH” as appropriate) n times. Specifically, the eNB 200 performs therepetition of the same signal (control information) by using nconsecutive subframes. Then, the eNB 200 repeatedly transmits the PDSCHm times in a second period T2. Specifically, the eNB 200 performs therepetition of the same signal (data) by using m consecutive subframes.One subframe is provided as a third period T3 for switching between thefirst period T1 and the second period T2. The third period T3 may be adecoding period used by the UE 100 to decode the control information.The third period T3 may be an RF adjustment period used by the UE 100 toswitch the frequency. The third period T3 having one subframe may beprovided also after the second period T2. It is noted that the onesubframe after the second period T2 may not be included in the thirdperiod T3.

Under such a premise, the eNB 200 configures, as the DRX cycle, a timeequal to or longer than a total of the first period T1, the secondperiod T2, and the third period T3 (one or two subframes), for the UE100. With such configuration, it is possible to wake up the UE 100 inaccordance with the repetition, and therefore, low delay transmissioncan be performed. In addition, occurrence of unnecessary Active Time(M/NPDCCH monitor) can be prevented while the UE 100 is receiving the(M/N) PDCCH or PDSCH. Further, for example, it is possible to avoid asituation where the Active Time arrives to force monitoring of the (M/N)PDCCH while the UE 100 is receiving the PDSCH. It is noted that if theDRX cycle less than the total of the first period T1, the second periodT2, and the third period T3 (one or two subframes) is configured, the UE100 may consider this configuration as a configuration error.

Modification of Second Embodiment

A modification of the second embodiment will be described with a focuson differences from the second embodiment. In the present modification,a case is mainly assumed where a DRX cycle less than a total of thefirst period T1, the second period T2, and the third period T3 (one ortwo subframes) is configured.

The UE 100 according to the modification of the second embodimentreceives the MBMS service provided using the SC-PTM transmission. Thecontroller 130 of the UE 100 uses the DRX cycle for the MBMS service toperform a DRX operation of intermittently monitoring the (M/N) PDCCHwhich transmits the control information corresponding to data belongingto the MBMS service. The receiver 110 of the UE 100 performs a firstrepeated reception of repeatedly receiving the control information and asecond repeated reception of repeatedly receiving the data. The DRXcycle includes a monitoring period requiring monitoring of the (M/N)PDCCH and a non-monitoring period not requiring the monitoring of the(M/N) PDCCH. The monitoring period corresponds to the Active Time. Thecontroller 130 of the UE 100 controls not to monitor the (M/N) PDCCHeven during the monitoring period while performing the second repeatedreception (that is, during the PDSCH reception). In other words, for thecurrently received TMGI, the UE 100 is exempted from monitoring of the(M/N) PDCCH if the UE 100 is receiving the PDSCH.

FIG. 18 is a diagram illustrating an example of an operation accordingto the modification of the second embodiment. As illustrated in FIG. 18,the eNB 200 uses the SC-MTCH to transmit data belonging to apredetermined MBMS service (here, the MBMS service of TMGI #1) to the UE100. Specifically, the eNB 200 repeatedly transmits the (M/N) PDCCH ntimes and repeatedly transmits the PDSCH m times. Here, the UE 100 isconfigured with a DRX cycle shorter than the DRX cycle as described inthe second embodiment. Therefore, a monitoring period occurs while theUE 100 is receiving the PDSCH. In such a case, the UE 100 receiving thePDSCH corresponding to a predetermined MBMS service is exempted frommonitoring the (M/N) PDCCH corresponding to the predetermined MBMSservice. Thus, the UE 100 can perform the PDSCH reception during themonitoring period. It is noted that the UE 100 may perform the (M/N)PDCCH reception, if the monitoring period occurs during the (M/N) PDCCHreception.

Here, although the (M/N) PDCCH and the PDSCH of the same MBMS service(the same TMGI) are described, the UE 100 may receive a plurality ofMBMS services (for example, TMGI #1 and TMGI #2). If the monitoringperiod corresponding to another MBMS service (TMGI #2) occurs duringreception of the PDSCH corresponding to a predetermined MBMS service(TMGI #1), the UE 100 may select one of the PDSCH reception and the(M/N) PDCCH reception. For example, the UE 100 may select an MBMSservice (TMGI) more prioritized by a user (application). If the PDSCHreception is selected, the UE 100 performs the PDSCH reception. On theother hand, if the (M/N) PDCCH reception is selected, the UE 100switches from the PDSCH reception to the (M/N) PDCCH reception.

Third Embodiment

A third embodiment will be described with a focus on a difference fromthe first and second embodiments. The third embodiment is an embodimentfor a stop indication in which the eNB 200 notifies the UE 100 of a stopof providing the MBMS service. Such a stop indication may be referred toas “RAN level stop indication”. Specifically, when transmitting the databelonging to the MBMS service to the UE 100 over the SC-MTCH, the eNB200 notifies the UE 100 of the stop of providing the MBMS service. Thestop indication may be included in the control information (DCI) to betransmitted over the (M/N) PDCCH. The stop indication may be included ina MAC control element (MAC CE) to be transmitted over the PDSCH. Below,a case is mainly assumed where the stop indication is transmitted by theMAC CE, but the stop indication may be transmitted by controlinformation (DCI). The stop indication may be included in an RRCmessage.

If the UE 100 fails to receive the stop indication, the UE 100 willwastefully attempt to receive the MBMS service that is stopped frombeing provided, which may cause unnecessary power consumption. The thirdembodiment is an embodiment aiming to solve such a problem.

The eNB 200 according to the third embodiment provides the MBMS serviceby using the SC-PTM transmission. The transmitter 210 of the eNB 200transmits data belonging to the MBMS service to the UE 100 by using theSC-MTCH. The controller 230 of the eNB 200 determines to stop theprovision of the MBMS service. The transmitter 210 of the eNB 200transmits, to the UE 100, the stop indication regarding the stop ofproviding the MBMS service a plurality of times. If the stop indicationis transmitted to the UE 100 a plurality of times, the UE 100 canreceive the stop indication more reliably than when the UE 100 transmitsthe stop indication only once.

The transmitter 210 of the eNB 200 transmits, at least once, the stopindication indicating that the provision of the MBMS service (MBMS data)is stopped before stopping the provision of the MBMS service. The stopindication may include time information indicating a time until theprovision of the MBMS service is stopped. The time information may beinformation in which the time until an end of data transmission isexpressed by the remaining transmission count of the SC-MTCH. Theremaining transmission count of the SC-MTCH may be the transmissioncount in no consideration of the repetition in the physical layer. Theremaining transmission count of the SC-MTCH may be the transmissioncount in consideration of the repetition. The time information may beinformation in which the time until the end of data transmission isexpressed by the number of subframes. If the stop indication istransmitted plurality of times before stopping the provision of the MBMSservice, a remaining time will decrease as the provision stop time ofthe MBMS service approaches. FIG. 19 is a diagram illustrating a casewhere the stop indication is transmitted by the MAC CE. The timeinformation is included in the MAC CE. As illustrated in FIG. 19, theMAC CE includes a one-octet stop indication. The stop indicationincludes the time information indicating the time until the provision ofthe MBMS service is stopped.

After stopping the provision of the MBMS service, the transmitter 210 ofthe eNB 200 may further transmit, to the UE 100, the stop indicationindicating that the provision of the MBMS service is stopped. The stopindication may be configured to be distinguishable from the stopindication before stopping the provision of the MBMS service. The stopindication may be transmitted alone without the MBMS data. For example,the MAC CE including the stop indication corresponding to apredetermined MBMS service is transmitted in a monitoring periodcorresponding to the predetermined MBMS service.

The transmitter 210 of the eNB 200 may repeatedly transmit the stopindication by performing the repetition of the physical channelcorresponding to the SC-MTCH. The physical channel may be the (M/N)PDCCH or the PDSCH. The repetition count of the physical channel used totransmit the stop indication may be greater than the repetition count ofthe physical channel not used to transmit the stop indication.Alternatively, only the physical channel used to transmit the stopindication may be repeatedly transmitted, and the repetition may not beapplied to the physical channel not used to transmit the stopindication.

FIG. 20 is a flowchart illustrating an example of an operation accordingto the third embodiment. Here, three operation examples (operationexamples 1 to 3) will be described. The PDCCH illustrated in FIG. 20means the (M/N) PDCCH. The SC-MTCH illustrated in FIG. 20 means thePDSCH corresponding to the SC-MTCH. The SC-MCCH stop timing illustratedin FIG. 20 means a timing at which the provision of the MBMS service isstopped. The eNB 200 performs the repetition of each of the (M/N) PDCCHand the PDSCH. One SC-MTCH transmission is comprised of an (M/N) PDCCHrepetition and a PDSCH repetition following the (M/N) PDCCH repetitionin the physical layer.

As illustrated in FIG. 20(a), in the operation example 1 (Option 1), therepetition count of the PDSCH to be used to transmit the stop indication(Stop ind) is greater than the repetition count of the PDSCH not to beused to transmit the stop indication. For example, the repetition countof the PDSCH not to be used to transmit the stop indication is three.The repetition count of the PDSCH to be used to transmit the stopindication is five. FIG. 20(a) illustrates an example in which therepetition count of the (M/N) PDCCH to be used to transmit the stopindication (Stop ind) is also increased. Further, an example oftransmitting the stop indication at the time of a final SC-MTCHtransmission is illustrated. In the operation example 1 (Option 1), theeNB 200 may notify the UE 100, over the SC-MCCH, of a time position ofthe SC-MTCH in which the repetition count is also increased.

As illustrated in FIG. 20 (b), in the operation example 2 (Option 2),the eNB 200 transmits the stop indications a plurality of times beforestopping the provision of the MBMS service. Each of the stop indicationsincludes the time information in which the time until the end of thedata transmission is expressed by the remaining transmission count ofthe SC-MTCH.

As illustrated in FIG. 20(c), in the operation example 3 (Option 3), theeNB 200 transmits the stop indication indicating that the provision ofthe MBMS service is stopped after stopping the provision of the MBMSservice. FIG. 20(c) illustrates an example in which the stop indicationis transmitted alone without the MBMS data.

Other Embodiments

In the above-described embodiments, the MBMS scenario using the SC-PTMtransmission is mainly assumed, but an MBMS scenario using MBSFNtransmission may also be assumed. As an example, in the above-describedembodiments, the SC-PTM transmission may be replaced with the MBSFNtransmission, the SC-MCCH may be replaced with the MCCH, and the SC-MTCHmay be replaced with the MTCH.

Each of the above-described embodiments may be implementedindependently; two or more embodiments may be combined and implemented.For example, a part of the process according to one embodiment may beadded to another embodiment. Alternatively, a part of the processaccording to one embodiment may be replaced with a part of aconfiguration of another embodiment.

In the above-described embodiments, a delivery of firmware is assumed asthe MBMS service. However, an MBMS service such as a group messagedelivery, a group chat message delivery, a delivery of a virusdefinition file, a scheduled update file delivery such as a weatherforecast, an unscheduled file delivery such as a news bulletin, anighttime file delivery (off peak delivery) such as a video content, anaudio/video streaming delivery, a telephone/video phone (groupcommunication), a live video delivery, and a radio audio delivery may beassumed.

A program for causing a computer to execute each process performed bythe UE 100 and the eNB 200 may be provided. Further, the program may berecorded on a computer-readable medium. If the computer-readable mediumis used, it is possible to install the program in a computer. Here, thecomputer-readable medium recording therein the program may be anon-transitory recording medium. The non-transitory recording medium isnot particularly limited; the non-transitory recording medium mayinclude a recording medium such as a CD-ROM or a DVD-ROM, for example. Achip set may be provided which includes: a memory in which a program forperforming each process performed by the UE 100 and the eNB 200 isstored; and a processor for executing the program stored in the memory.

In the above-described embodiments, the LTE system is exemplified as themobile communication system. However, the present disclosure is notlimited to the LTE system. The present disclosure may be applied to amobile communication system other than the LTE system.

[Supplementary Note]

1. Introduction

In this supplementary note, the issues being concerned are discussed.

2. Discussion

(2.1. RAN Level Stop Indication)

Discussion point 1 was that “Companies are invited to provide theirviews on how to indicate the RAN-level stop for SC-PTM service in NB-IoTand FeMTC”. As the rapporteur summarized, the visible alternatives tocarry RAN level stop indication are DCI of SC-MCCH scheduling and MACCE.

Regarding DCI, it's conceptually aligned with the 2-bit notification foron-going service which RAN2 agreed, i.e., “whether the configuration ofthe SC-MTCH will be changed in next MP” and “whether the new servicesare due to start in next MP”. The 1-bit indication in DCI may bebeneficial from the overhead point of view, but the 1-bit does need tobe transmitted even when the indication is not necessary, i.e., thedefined bit is in every PDCCH and every repetition. However, thedrawback of this option is the potential impact to RAN1.

Regarding MAC CE, it's seen as the straightforward solution since thereis already the similar MAC CE for MBSFN, i.e., (Extended) MCH SchedulingInformation (MSI). The benefit of this option is flexibility from theperspective of scalability, e.g., no scheduling of MAC CE in SC-MTCHwhen unnecessary, ability of (future) extensions and so on. However, thesignalling overhead may be of concern, i.e., the byte-aligned MAC SDUand corresponding MAC sub-header.

Observation 1: There are two visible alternatives for RAN level stopindication, 1-bit in DCI or MAC CE.

Before deciding on how the stop indication should be provided, it'sworth discussing whether RAN level stop indication is provided only onceor multiple times, wherein the 1-bit option seems to imply the“one-shot” indication (excluding the PDCCH/PDSCH repetitions forEnhanced Coverage) that is likely provided in the last SC-MTCHtransmission(s). However, it should be assumed that there is noguarantee the UE can receive any of the SC-MTCH transmissions includingthe last one with the stop indication, due to e.g., temporally bad radioconditions and/or the lack of feedback. If such a one-shot indication isassumed, the UE may continue to monitor SC-MTCH until the next SC-MCCHmodification boundary (i.e., to remove the corresponding configurationfrom SC-MCCH), even though the SC-MTCH transmission has already ended.It can be a serious problem considering the SC-MCCH modification periodis extended and power consumption is critical for such UEs (i.e.,FeMTC/eNB-IoT). To avoid such an undesirable condition, the eNB mayprovide the repetition of RAN level stop indication.

Observation 2: The UE, which cannot receive RAN level stop indication,will need to continue SC-MTCH monitoring, even if the SC-MTCHtransmissions have already stopped.

Proposal 1: RAN2 should discuss whether the repetition of RAN level stopindication is necessary.

If Proposal 1 is acceptable, the three options could be considered forthe repetition of RAN level stop indication as follows (refer to FIG.20);

Option 1: The number of PDCCH/PDSCH repetitions (for Enhanced Coverage)is increased only for SC-MTCH with RAN level stop indication;

This option reuses the existing repetition mechanism for EnhancedCoverage; that is the eNB increases number of PDCCH/PDSCH repetitionsfor SC-MTCH only when it includes RAN level stop indication. The benefitof this option is that no standard impact is expected, e.g., the maximumnumber of repetitions with relatively larger value can be configured inadvance without further specification change. The drawback may beunnecessary repetition of payload and a sort term repetition.

Option 2: RAN level stop indication is repeatedly provided over severalSC-MTCHs until it stops;

This option assumes RAN level stop indication is provided in multipleSC-MTCH occasions, e.g., (n−2), (n−1) and (n), whereby “n” means thelast SC-MTCH transmission with the stop indication. The benefit is thata better time-domain diversity gain is expected by means of relativelylong term repetition. The drawback is the UE needs to know when theSC-MTCH actually stops, so some sort of “count-down” mechanism isnecessary which may be similar to the existing “Stop MTCH” in MSI,whereby “Stop MTCH” was introduced for the other purpose, i.e., UE'sinternal preparation for service continuity.

Option 3: RAN level stop indication is repeatedly provided after SC-MTCHstops.

This option assumes RAN level stop indication is provided even after thepayload transmission ends, i.e., in the remaining SC-MTCH schedulingperiods until the next SC-MCCH modification period. The benefit is agood diversity gain similar to Option 2, and there is no need for the“count-down” mechanism. The drawback is the signalling overhead that maybe increased due to the repetition of M/NPDCCH necessary for the RANlevel stop indication.

Based on the considerations above, Option 2 seems to provide the mosteffective way to improve the reliability of RAN level stop indicationreception, while it may be left up to NW implementation which option isused in more than one option is allowed. In this sense, the MAC CEdiscussed in Observation 1 is slightly preferable since it couldpotentially cover all options above and even for the case whenrepetition of stop indication is not provided (refer to FIG. 19).

Proposal 2: RAN2 should agree to use MAC CE for RAN level stopindication.

Proposal 3: RAN2 should discuss whether the “count-down” mechanism isnecessary in RAN level stop indication, in order to allow repetition ofRAN level stop indication.

(2.2. Ranking-Based Cell Reselection)

(2.2.1. Offset)

It was agreed that “For feMTC, for UE in enhanced coverage, an offset toSC-PTM cells in ranking based cell reselection is used if SC-PTM cellexists and UE is receiving or interested to receive an MBMS service” and“For NB-IoT, an offset to SC-PTM cells in ranking based cell reselectionis used if SC-PTM cell exists and UE is receiving or interested toreceive an MBMS service”. In addition, it was discussed how the offsetshould be provided. But the value range of the offset has not beendiscussed.

According to the discussion, it is commented that “Option1 is a similarway and allows some flexibility to the network to configure the cellreselection criterion, such as a small offset to avoid that UE reselectsthe SC-PTM cell which has low RSRP regardless of other non-SC-PTM cellswhich has much higher RSRP.” However, it's still unclear how the “smalloffset” works.

For example, if the UE is located in Enhanced Coverage on SC-PTM layerand also close to a cell on non-SC-PTM layer (as illustrated in FIG.13), the UE will likely reselect the cell on non-SC-PTM layer when theoffset is not configured. Even if it's configured, the question is howmuch offset would work for the intended result of cell reselectionprocedure, i.e., 5 dB, 10 dB or 20 dB? Regardless of the value selected,it's impossible to prevent all the UEs from reselecting a cell onnon-SC-PTM layer under all scenarios, i.e., since it's matter ofprobability where the UE is located and how the cells are configured.Consequently, UEs that ends up reselecting a cell on the non-SC-PTMlayer will need to establish RRC Connection to acquire the MBMS serviceof interest, i.e., via unicast, which is undesirable from the UE powerconsumption perspective and may potentially increase NW congestion dueto massive number of MTC devices e.g., for IoT. Although FIG. 13 depictsthe inter-frequency case for simplicity, the scenario is also applicableto the intra-frequency case wherein the condition becomes even moreserious.

So, the proponents of ranking-based cell reselection have to clarify thevalue range of the offset.

Observation 3: It's unclear how much of an offset needs to be defined.

In Rel-13 the UEs should be allowed to prioritize SC-PTM cells as muchas possible, to bypass the ranking criteria set forth by the eNB sincethe reception of SC-PTM transmission was considered to be of higherpriority. But NB-IoT UEs don't have the priority handling procedure.

As discussed, it is considered one of solutions could be considered toallow the configuration of (minus) infinity value as one of the offsetvalues. With this configuration, it can be ensured that all UEs will beable reselect the cell on SC-PTM layer as long as a suitable cellexists, even if it's an NB-IoT-UE. So, the operator can allow UEs toprioritize SC-PTM within the constraint of the ranking procedure.Therefore, at least the (minus) infinity value is worth introducing as aconfiguration option of the offset.

Proposal 4: RAN2 should agree to have the configuration option with(minus) infinity, for the offset of ranking-based cell reselection.

(2.2.2. Cell Reselection Before RRC Connection Request)

In Rel-13, the ranking-based cell reselection was introduced even forintra-frequency case. It's quite useful for unicast, since the UE thatreselects a cell that offers normal coverage minimizes the resourceconsumption after transitioning to RRC Connected with e.g., linkadaptation. It works as a “static” scenario.

In Rel-14, it's extended for SC-PTM with the offset, whichimproves/ensures the UE reselects a cell providing SC-PTM as much aspossible.

It could be considered as a “dynamic” scenario that the UE currentlyreceiving SC-PTM from the cell which is not suitable for unicast, e.g.,the UE is in Enhanced Coverage of this cell. When MT/MO call occurs, theUE would stop receiving SC-PTM and initiate RRC Connection Request,since SC-PTM is only supported in IDLE.

It may be expected that the UE would have already reselected the bestranked cell for unicast if it's no longer interested in SC-PTM, i.e.,stop receiving SC-PTM. However, it should be considered how the UEshould behave in case the UE decides to initiate Unicast service whileSC-PTM is still ongoing, and while the UE is within the EnhancedCoverage. If the offset is still applied this may lead to the problemthat the UE may end up initiating Unicast service on a less than optimumcell. Therefore, preferably, the UE should perform the cell reselectionwithout the offset just before RRC Connection Request. However, in the“dynamic” scenario after the UE's no longer interested in receivingSC-PTM, since the cell reselection is somewhat a slow process, e.g., interms of measurements, the UE would not be expected to acquire the mostsuitable cell quickly. Considering MBMS in Enhanced Coverage is firstdiscussed in Rel-14, RAN2 should discuss whether to specify the intendedUE behaviour for reselection just before initiating RRC ConnectionRequest. Note that some UE implementation may perform such a fastre-evaluation assuming it only removes the offset.

Proposal 5: RAN2 should discuss whether to define the UE behaviour forcell reselection immediately after it stops receiving SC-PTM but justbefore RRC Connection Request.

(2.3. MBMS Interest Indication)

In Rel-14, SC-PTM reception is supported only in IDLE. It means that theUE in Connected needs to be released to IDLE, in order to receive MBMSservice of interest via SC-PTM. However, the eNB doesn't know whetherthe UE needs to prioritize SC-PTM over unicast. It may result in e.g.,additional UE battery consumption and/or NW congestion, although it maybe assumed the UE, especially in eNB-IoT, typically stays in Connectedfor a very short time.

To make sure the optimal RRC state control for FeMTC/eNB-IoT, theexisting MBMS Interest Indication could be reused, i.e., withmbms-Priority, which was intended for mobility control in the legacyreleases. For example, the eNB may or may not decide to release RRCConnection when it receives the UE's prioritization between SC-PTM andunicast. So, MBMS Interest Indication should be supported inFeMTC/eNB-IoT.

Proposal 6: RAN2 should agree that MBMS Interest Indication is supportedin FeMTC and eNB-IoT.

If Proposal 6 is agreeable, it could be achieved with editorialextensions, i.e., to capture SIB15-NB and SIB20-NB into the existingprocedural specification.

(2.4. M/NPDCCH Configuration)

Currently, MPDCCH configuration is configured via dedicated signalling,i.e., as part of EPDCCH-Config and NPDCCH configuration is also, i.e.,NPDCCH-ConfigDedicated-NB. However, it does not work since SC-PTM may bereceived only by UEs in RRC IDLE. So, these configurations need to bebroadcasted for SC-PTM reception.

As suggested in the current running CR of TS 36.331, M/NPDCCHconfiguration should be broadcasted in SIB20 for SC-MCCH, and in SC-MCCHfor SC-MTCH.

Proposal 7: RAN2 should agree to introduce MPDCCH/NPDCCH configurationsare provided in SIB20 and SC-MCCH, for reception of SC-MCCH and SC-MTCHrespectively.

The invention claimed is:
 1. A user equipment for receiving a MultimediaBroadcast Multicast Service (MBMS) service provided using Single CellPoint-To-Multipoint (SC-PTM) transmission, comprising: a processor and amemory coupled to the processor, wherein the processor is configured toperform a cell reselection operation of selecting a cell to be used as aserving cell of the user equipment while the user equipment is in aRadio Resource Control (RRC) idle mode, in the cell reselectionoperation, select, as the serving cell, a cell having a highest rankingdetermined based on a radio quality and an offset from among a pluralityof cells, determine that the user equipment is in an enhanced coverageof a cell if a first cell selection criterion S for normal coverage isnot fulfilled for the cell and a second cell selection criterion S forenhanced coverage is fulfilled for the cell, in the cell reselectionoperation, when determining that the user equipment is in the enhancedcoverage of a cell, use an infinite offset as the offset to be appliedto a cell where the MBMS service is provided by the SC-PTM transmission,in response to a predetermined condition for the SC-PTM transmissionbeing satisfied.
 2. The user equipment according to claim 1, wherein thepredetermined condition includes the user equipment receiving or beinginterested in receiving the MBMS service.
 3. The user equipmentaccording to claim 1, wherein the processor is configured to receive asystem information block broadcast from the serving cell, and the systeminformation block includes information for the user equipment todetermine whether to use the infinite offset when the user equipment isin the enhanced coverage.
 4. The user equipment according to claim 1,wherein the processor is configured to when the user equipment is in theenhanced coverage, perform the cell reselection without consideringfrequency priorities.
 5. An apparatus provided in a user equipment forreceiving a Multimedia Broadcast Multicast Service (MBMS) serviceprovided using Single Cell Point-To-Multipoint (SC-PTM) transmission,the apparatus comprising: a processor and a memory coupled to theprocessor, the processor is configured to perform a cell reselectionoperation of selecting a cell to be used as a serving cell of the userequipment while the user equipment is in a Radio Resource Control (RRC)idle mode, in the cell reselection operation, select, as the servingcell, a cell having a highest ranking determined based on a radioquality and an offset from among a plurality of cells, determine thatthe user equipment is in an enhanced coverage of a cell if a first cellselection criterion S for normal coverage is not fulfilled for the celland a second cell selection criterion S for enhanced coverage isfulfilled for the cell, and in the cell reselection operation, whendetermining that the user equipment is in the enhanced coverage of acell, use an infinite offset as the offset to be applied to a cell wherethe MBMS service is provided by the SC-PTM transmission, in response toa predetermined condition for the SC-PTM transmission being satisfied.6. A method for use in a user equipment for receiving a MultimediaBroadcast Multicast Service (MBMS) service provided using Single CellPoint-To-Multipoint (SC-PTM) transmission, comprising performing a cellreselection operation of selecting a cell to be used as a serving cellof the user equipment while the user equipment is in a Radio ResourceControl (RRC) idle mode, in the cell reselection operation, selecting,as the serving cell, a cell having a highest ranking determined based ona radio quality and an offset from among a plurality of cells,determining that the user equipment is in an enhanced coverage of a cellif a first cell selection criterion S for normal coverage is notfulfilled for the cell and a second cell selection criterion S forenhanced coverage is fulfilled for the cell, and in the cell reselectionoperation, when determining that the user equipment is in the enhancedcoverage of a cell, using an infinite offset as the offset to be appliedto a cell where the MBMS service is provided by the SC-PTM transmission,in response to a predetermined condition for the SC-PTM transmissionbeing satisfied.